During the past 20 years, a variety of prostaglandin derivatives have been synthesized and isolated from natural sources. The compounds are generally quite potent and possess a variety of pharmacological properties. See Nelson, et al., Chemical and Engineering News, 30 (Aug. 16, 1982). See also "Practical Applications of Prostaglandins", (S. M. M. Karim, Ed.), University Park Press, Baltimore, 1979. Many prostaglandins which either have interesting biological properties or are intermediates to other prostaglandins have been isolated from marine animals such as coral. See W. P. Schneider in "Prostaglandins: Chemical and Biochemical Aspects", p. 4, University Park Press, Baltimore, 1976; Nelson, et al., supra, at page 32; H. Kikuchi, et al., Tetrahedron Letters, 23 (49), 5171 (1982). Since small changes in chemical structure have been shown to produce large differences in biological potency and utility, new derivatives of prostaglandins hold the promise that useful drugs may be found.